Abstract： Objective To investigate the correlation between the improvement of insulin resistance(IR)and T lymphocyte subsets in patients with type 2 diabetes mellitus(T2DM)after intensive insulin therapy.Methods A total of 160 patients with T2DM who were treated in the endocrinology department of our hospital from February 2020 to March 2023 were selected.They were divided into simple T2DM group(n=80)and T2DM combined with family history of diabetes mellitus(FHD)group(n=80)based on whether they had FHD.The changes in blood glucose,pancreatic islet cell function,T lymphocyte subsets,and inflammatory cytokine levels were compared before and after treatment between the two groups.Pearson correlation analysis was used to investigate the correlation between insulin resistance index(HOMA-IR)and T lymphocyte subsets,and multiple linear regression analysis was used to explore the influencing factors for IR in T2DM patients.Results After treatment,the FPG,2 hPG,and coefficient of variation(CV)of blood glucose were lower than before treatment in the T2DM group(P<0.05).In the FHD group,the FPG,2 hPG,bedtime blood glucose,and CV were lower after treatment than before treatment(P<0.05).After treatment,the FPG,2 hPG,and CV were lower in T2DM group than in FHD group(P<0.05).After treatment,FC-P,2 hC-P,HOMA-β and IL-10 were higher(P<0.05),while HOMA-IR,IL-21,IL-1β,CD3+,CD4+,CD8+,CD4+/CD8+were lower than before treatment in both groups(P<0.05).After treatment,FC-P,2 hC-P,HOMA-β and IL-10 were higher,while HOMA-IR,IL-21,IL-1β,CD3+,CD4+,CD8+,CD4+/CD8+were lower in T2DM group than in FHD group(P<0.05).Pearson correlation analysis showed that HOMA-IR was positively correlated with CD3+,CD4+,CD8+,CD4+/CD8+(P<0.05).Multiple linear regression analysis shows that BMI and CD8+are influencing factors for IR in T2DM patients.Conclusions Intensive insulin therapy can improve the islets β cell function inpatients with T2DM and IR.There is a correlation between IR and the increase of CD8+T lymphocyte level in patients.